Experiments are being conducted on model membranes, phospholipid bilayers, to investigate the molecular basis for the action of local anesthetics and salicylates on nerve. Local anesthetics are known to block nerve conduction by decreasing the cation conductance while the salicylates, conversely, are known to increase the cation and decrease the anion conductance of a single nerve fiber. The local anesthetics and salicylates bear a positive and negative charge respectively and the above results could be due to an adsorption of these molecules to the nerve membrane and a concomitant change in the electric potential at the surface of the membrane. To investigate this possibility, bilayer membranes have been formed from the major neutral and negatively charged phospholipids found in nerve membranes and the change in surface potential produced by the adsorption of these drugs has been determined. The results obtained with salicylate have been published. Both the absolute and relative effectiveness of the local anesthetics investigated to date (dibucaine greater than tetracaine greater than butacaine greater than xylacaine greater than procaine) are quantitatively consistent with their effects on nerve membranes. It has been shown that the forces involved in the adsorption of the anesthetics are "hydrophobic" in nature, that a bilayer and a nerve respond in an identical manner to a change in pH in the presence of a local anesthetic and that the long duration of action of the more potent anesthetics can be mimicked on bilayers. A theoretical study concerned with the distribution of charges in a bilayer has been published, (McLaughlin and Harary, Biophys).